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Assay Method Information

Assay Name:  In Vitro Assay
Description:  The assay is using the PathHunter CHO-K1 CXCR7 β-arrestin cell line from DiscoverX. The system is based on the Enzyme Fragment Complementation Technology. Two complementing fragments of the β-galactosidase enzyme are expressed within stably transfected cells. The larger portion of β-gal, termed EA for Enzyme Acceptor, is fused to the C-terminus of b-arrestin 2. The smaller fragment, termed ProLinkż tag, is fused to CXCR7 at the C-terminus. Upon activation, b-arrestin is recruited which forces the interaction of ProLink and EA, allowing complementation of the two fragments of b-gal and the formation of a functional enzyme which is capable of hydrolysing the substrate and generating a chemiluminescent signal. CHO-K1 CXCR7 β-arrestin cells are detached from culture dishes with a cell dissociation buffer (Invitrogen, #13151-014) and collected in growing medium (F12 HAMS 90% (v/v)/FCS 10% (v/v), Penicillin/streptomycin 1% (v/v)). 5000 cells per well (in 20 μl) are seeded in a 384 well plate (white-walled, clear bottom; BD Falcon #353274). The plate is incubated at 37° C./5% CO2 for 24 hours. Medium is then replaced by 20 μl OPTIMEM (Invitrogen #31985) for 3 to 4 hours. Test compounds are dissolved at 10 mM in DMSO and serially diluted in DMSO to 200× of the final concentration for dose response curves. Compounds are then diluted 1:33.3 in HBSS1X. 5 μl/well of HBSS1X/20 mM HEPES/0.2% BSA are added to the assay plate followed by addition of 5 μl/well of diluted compounds. CXCL12 (Peprotech #300-28A) may be used as a reference agonist. The plate is incubated for 90 minutes at 37° C. 12 μl of detection reagent (Path Hunter Detection Kit, DiscoveRx, #93-0001) is transferred to the assay plate and to the plate is incubated for 1 hour at room temperature. Luminescent signal is read in a microplate reader (FLUOstar Optima, bmg). The calculated EC50 values may fluctuate depending on the daily cellular assay performance. Fluctuations of this kind are known to those skilled in the art. Average EC50 values from several measurements are given as geometric mean values.
Affinity data for this assay
 

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Last update November 1, 2007
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